Magnesium base alloy



Patented July 26, 1938 PATENT OFFICE MAGNESIUM BASE ALLOY John A. Gann, Midland, Mich, assignorto The Dow Chemical Company, Midland, Micln, a corporation oi. Michigan No Drawing. Original application-August 2, 1937, Serial No. 156,941. Divided and this applica-.

tion February 3, 1938, Serial N 0. 188,462

4 Claims.

The present invention relates to magnesium alloys and more particularly to those in which magnesium is the predominant constituent.

A large number of magnesium alloys have been developed and many of them have been used commercially. While certain of these alloys have.

tensile strengths that are satisfactory for a wide variety of uses, their yield strengths are often so low that articles made. from such alloys will deform readily and assume a large permanent set at a stress considerably below the stress corresponding to the ultimate tensile strength.

The principalobject of my invention is to produce magnesium alloys having improved physical properties. A more specific objectis to produce magnesium alloys having improved ratios of yield strength to tensile strength. Other objects and advantages will appear as the description proceeds.

This invention is based on the discovery that the magnesium-aluminum-cadmium alloys, as described in United States Patent, No. 1,729,339, may be improved to a very marked extent by the addition of relatively small amounts of lead and that this alloy may be still further improved by the addition of relatively small amountsoi at least one'of the metals selected from the group, tin and zinc. I have likewise discovered that maximum property improvement is obtained when these alloys are subjected to the well known methods of solution heat treatment and aging. I have found that these advantages occur when approximately 0.5 to 10 per cent of lead is added to the known magnesium-aluminumcadmium alloy containing 1 to 12 per cent of aluminum and 1 to 10 per cent of cadmium,

thereby producing my new magnesium-aluminum-cadmium-lead alloy. I'have likewise discovered that the properties of this magnesium-, aluminum-cadmium-lead alloy may be improved by adding approximately 0.5 to 8 per cent of at least one of the metals selected from the group of relatively low melting-point metals, tin and zinc.

The following tables give specific examples which illustrate the improvement in yieldstrength and in the ratio of yield strength to tensile strength 01' my new. alloy as compared to the known magnesium-aluminum-cadmium alloys. I have likewise found that the increase in yield strength and in the yield strength to tensile strength ratio, as given in these tables, is accompanied by an improvement in Brinell hardness amounting to approximately 25 per cent for the as cast alloys, 35 per cent for the solution heat treated alloys, and 55.per cent for the solution heat treated andv aged alloys.

Cast alloys Nominal com sition 9 f, Yield Tensile 33 mam er) strength, strength, strength lb./s(1.1n. lb./sq. in. to tensile A] 03 Pb Sn Zn strength Solution Mat treatad alloys 2 s 5,000 25,000 .23 2 a 10 7,000 20,000 .00 2 s 10 2 0,000 20,000 .32 Q 4 4 7,000 3,000 .25 I 4 4 2 0,300 20,000 \20 30. 0 4 2 0,000 30,300 .30 0 4 2 0 12,400 20,000 .42 0 4 2 13,100 35,000 .37 0 .4 2 0 15,000 20,700 .53 s 2 11,500 32,000 .30 s 2 1 4 15,300 32,500 .47 s 2 1 3 4 10,300 20,000 .55 s 2 1 5 4 17,200 20,000 .00 4 0 0 2 3 12,400 27,200 .45

Solutionlmttreated and and alloys 40 2 0 0,100 20,000 .23 2 s- 10 3,100 25,000 .31 2 s 10 2 10,200 25,000 .41 4 4 7,200 20,500 .25 4 4 2 7,700 20,000 .27 0 4 2 10,100 31,100 .32 5 0 4 2 0 13,000 30,300 .45 0 4 2 10,000 34,300 .52 ,0 4 2' 0 23,3 20,000 .02 s 2 14,200 32,000 .44 s 2 1 -4 23,200 35,400 .05 0 2 1 4 23,500 33,000 .70 0 2 1 5 4 23,300 32,200 .72 4 0 0 2 3 10,400 I 30,000 .55

The specific proportionsot each metal 'to be employed in these new alloys depends on the use for which the alloy is intended. In geperalrl fio prefer to use alloys containing more than 80 per cent of magnesium and less than 20 per cent of total added metals, but where the alloy is to be used for the productionof wrought shapes gen-' per cent of cadmium, 1 to 6 per cent of lead, 1 to 6 per cent of tin, and 1 to 4 per cent of zinc. For

the production of wrought shapes by extrusion and forging, the alloy should preferably contain 'to 96 per cent of magnesium and the various alloying ingredients in the following proportions: 1 to 8 per cent of aluminum, 1 to 3 per cent of cadmium, 0.5 to 2 per cent of lead, 0.5 to 3 per cent of tin, and 0.5 to 2 per cent of zinc. If the alloy is to be fabricated by rolling rather than by extrusion'or forging, the percentage of aluminum should preferably lie within the range of 1 to 5 per cent.

My new polynary alloys may be prepared by the methods usually employed for melting and alloying metals with magnesium, such as adding the respective alloying metals singly or jointly to a bath of molten magnesium protected from oxidation by a cover of fluid flux. The solution heat treatment for the zinc-free alloys may consist in heating the material for 20 hours at 430 0., followed by air cooling, or, when zinc is present in 2,124,561 ment consists of approximately 16 hours heating at 0., subsequent to the above solution heat treatment. Plastic deformation operations, such' as extruding, forging, and rolling are best conducted at temperatures between 300 and 400 C.

This application is a division of my co-pending application Serial No. 156,941, filed August 2, 1937.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the ingredients and the steps herein disclosed, provided those stated by any of the following claims of cadmium, about 1 to 6 per cent of lead, about 1 to 6 per cent of tin, and about 1 to 4 per cent of zinc, the balance being magnesium.

3. A magnesium-base alloy containing about 1 to 8 per cent of aluminum, about 1 to 3 per cent of cadmium, about 0.5 to 2 per cent of lead, about 0.5 to 3 per cent ofv tin, and about 0.5 to 2 per cent of zinc, the balance .being magnesium. I

4. A magnesium-base alloy-containing about 8 percent of aluminum, 2 per cent of cadmium, 1 per cent of lead, 3 per cent of tin, and 4 per cent of zinc, the balance being magnesium.

JOHN A. GANN. 

